Chapter 6
Charge Carrier Dynamics in Polymer
Solar Cells
Hideo Ohkita
6.1 Introduction
Polymer solar cells have attracted increasing interest as a next-generation solar cell
because they have excellent advantages of colorful, flexible, lightweight, and especially high-throughput and low-cost production by printing techniques. Thus, they
have been intensively studied over the world for a long time. As a result, the power
conversion efficiency (PCE) has been steadily improved year by year in the last two
decades. In 1995, the PCE was less than 1% [1, 2]. Currently, the PCE is more than
17%, which was reported for tandem solar cells in 2018 [3] and is more than 18%,
which was reported for single-junction cells in 2020 [4]. This efficiency is even
higher than that of amorphous silicon solar cells.
These improvements are partly due to remarkable developments of various photovoltaic materials such as soluble fullerene derivatives like a [6,6]-phenyl-C 61 -butyric
acid methyl ester (PCBM) [5], crystalline conjugated polymers like a regioregular poly(3-hexylthiphene) (RR-P3HT) [6], low-bandgap conjugated polymers
like a poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b
]dithiophene)alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) [7], and non-fullerene acceptors like a 6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydro-dithieno[2,3-d:2
,3
-d
]s-indaceno[1,2-b:5,6-b
]dithiophene (ITIC) [8]. In other words, such diversity of
organic materials is one of the great advantages over inorganic solar cells. For
fullerene-based polymer solar cells, as described in Sect. 6.4, charge dissociation
is likely to be more efficient in polymer solar cells based on highly crystalline
conjugated polymers.
The original version of this chapter was revised: Greek symbol have been updated in the Equation 6.1.
The correction to this chapter is available at https://doi.org/10.1007/978-981-15-9113-6_11
H. Ohkita (B)
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura
Campus, Kyoto, Nishikyo-Ku 615-8510, Japan
e-mail: ohkita@photo.polym.kyoto-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2021, corrected publication 2021
M. Hiramoto and S. Izawa (eds.), Organic Solar Cells,
https://doi.org/10.1007/978-981-15-9113-6_6
123
Charge Carrier Dynamics in Polymer
Solar Cells
Hideo Ohkita
6.1 Introduction
Polymer solar cells have attracted increasing interest as a next-generation solar cell
because they have excellent advantages of colorful, flexible, lightweight, and especially high-throughput and low-cost production by printing techniques. Thus, they
have been intensively studied over the world for a long time. As a result, the power
conversion efficiency (PCE) has been steadily improved year by year in the last two
decades. In 1995, the PCE was less than 1% [1, 2]. Currently, the PCE is more than
17%, which was reported for tandem solar cells in 2018 [3] and is more than 18%,
which was reported for single-junction cells in 2020 [4]. This efficiency is even
higher than that of amorphous silicon solar cells.
These improvements are partly due to remarkable developments of various photovoltaic materials such as soluble fullerene derivatives like a [6,6]-phenyl-C 61 -butyric
acid methyl ester (PCBM) [5], crystalline conjugated polymers like a regioregular poly(3-hexylthiphene) (RR-P3HT) [6], low-bandgap conjugated polymers
like a poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b
]dithiophene)alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) [7], and non-fullerene acceptors like a 6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydro-dithieno[2,3-d:2
,3
-d
]s-indaceno[1,2-b:5,6-b
]dithiophene (ITIC) [8]. In other words, such diversity of
organic materials is one of the great advantages over inorganic solar cells. For
fullerene-based polymer solar cells, as described in Sect. 6.4, charge dissociation
is likely to be more efficient in polymer solar cells based on highly crystalline
conjugated polymers.
The original version of this chapter was revised: Greek symbol have been updated in the Equation 6.1.
The correction to this chapter is available at https://doi.org/10.1007/978-981-15-9113-6_11
H. Ohkita (B)
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura
Campus, Kyoto, Nishikyo-Ku 615-8510, Japan
e-mail: ohkita@photo.polym.kyoto-u.ac.jp
© Springer Nature Singapore Pte Ltd. 2021, corrected publication 2021
M. Hiramoto and S. Izawa (eds.), Organic Solar Cells,
https://doi.org/10.1007/978-981-15-9113-6_6
123